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Re: Special - Not for General Use

I find loose unused breakers in service panels quite often. Being that they are not connected or in use, I don't worry about them or give it a second thought. I just move on and look for the real concerns.

Re: Special - Not for General Use

It's probably an inverse-time breaker typically used for motor control circuits as opposed to a "typical" thermal magnetic breaker.

All molded case circuit breakers are INVERSE TIME circuit breakers (OK 99% of them). All this means is the higher the current the faster the CB trips.

Circuit breakers utilized in typical branch circuit wiring are thermal magnetic devices. That is thermal is the long time/overload portion, higher the current the faster the circuit breaker operates for over loads.

For thermal Such as a 20 am CB may carry 300% (60 amp) for 30 seconds
200% (40 amps) for 90 seconds
110% (22 amps) for days
All times are estimates/guesses as I do not have time curves available at this time, (there are in the office).

For Instantaneous Instantaneous occurs at multiples above 400% typically and operates on the same principle, the higher the current the faster the CB trips.

Inverse only CBs are normally part of a motor control stater or motor control center where the thermal (long time/overload) protects the motor against overloads, the inverse time is for fault protection and is sized to permit the motor to start (starting currents are typically 4-6 times). Inverse CBs have settings from 4-12 times normally that is for a 20 amp CB 80 to 240 amps.

Re: Special - Not for General Use

Good info Brad.
I was thinking that this may have simply been a manual/mechanical disconnect w/o any overcurrent or short circuit protection.
Kind of like those tap blocks in the form of a circuit breaker case used to feed some panels.

Re: Special - Not for General Use

I have some ITE BQ frame breakers (bolt -on type) that are marked in the same manner, the reason being they have 1/4" quick-disconnect terminals instead of the traditional lugs,they are intended for OEM use in equipment.

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